Activation Analysis of Aluminum from Water Extract of Soil
1973
Misra, U. K. | Graham, E. R. | Upchurch, W. J. | McKown, D. M.
Determination of low-level Al in soil water extracts or lysimeter leachings requires a method extremely sensitive in the ppb range. ₁₃²⁷Al(n,γ)₁₃²⁸Al is rapid and convenient because it has a high cross section and a short half life. ²⁸Al may also be produced by ₁₄²⁸Si(n,p)₁₃²⁸Al. Hence a correction must be made by determining Si colorimetrially and finding the counts due to Si from a standard graph of Si concentration vs. cpm in the channels used for Al. ³⁸Cl was the major interfering nuclide. Chloride was removed by leaching the extracts through anion exchange resin saturated with NO₃. ⁵⁶Manganese becomes an interfering nuclide in samples with high Mn content. Manganese corrections may be made by spectrum stripping. Aluminum standard solution was passed through an anion exchanger. Silica and aluminum standard solutions, and the sample extracts were then activated for 1 min. The samples were allowed to decay for 3 min. Then 1 ml was counted using a NaI (Tl) detector and a multichannel gamma ray analyzer. The Al content of the samples was determined and it appears that a coefficient of variation near 3.0% would be obtainable on samples down to 0.1 ppm.
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